سحابة هيلز

Artist's view of the Oort cloud, Hills cloud, and Kuiper belt (inset)

In astronomy, the Hills cloud (also called the inner Oort cloud[1] and inner cloud[2]) is a vast theoretical circumstellar disc, interior to the Oort cloud, whose outer border would be located at around 20,000 to 30,000 astronomical units (AU) from the Sun, and whose inner border, less well defined, is hypothetically located at 250–1500 AU,[بحاجة لمصدر] well beyond planetary and Kuiper Belt object orbits—but distances might be much greater. If it exists, the Hills cloud contains roughly 5 times as many comets as the Oort cloud.[3]

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Overview

History

Original Oort cloud model

Ernst Öpik



New model

Jack G. Hills, the astronomer who first proposed the Hills cloud



Characteristics

Structure and composition

Interior and exterior Oort cloud




Formation

Possible Hills cloud objects

Name Diameter
(km)
Perihelion
(AU)
Aphelion
(AU)
Discovery
2012 VP113 315 to 640 80٫5 445 2012
(90377) Sedna 995 to 1٬060 76٫1 935 2003
(87269) 2000 OO67 28 to 87 20٫8 1,014.2 2000
(308933) 2006 SQ372 50 to 100 24٫17 2,005.38 2006


Comets

Comet McNaught

Sedna, the first candidate

Animation of Sedna's orbit (in red) with the Hills cloud (in blue) at the last moment of the loop


Artist's impression of Sedna


2012 VP113

Trans-Neptunian object 2012 VP113 was announced on 26 March 2014 and has a similar orbit to Sedna with a perihelion point significantly detached from Neptune. Its orbit lies between 80 and 400 AU from the Sun.

الهوامش

المصادر

  1. ^ see Oort cloud
  2. ^ Villemin, Gérard. "Astronomie, astéroïdes et comètes" (in الفرنسية).
  3. ^ Duncan, Martin J.; Quinn, Thomas; Tremaine, Scott (1987). "The Formation and Extent of the Solar System Comet Cloud". The Astronomical Journal. 94: 1330. Bibcode:1987AJ.....94.1330D. doi:10.1086/114571.

قراءات إضافية


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وصلات خارجية